New research suggests that it may even delay the process of rebuilding muscles. Naomi Crystal, who led the study at the University of New Hampshire, found that ice baths interfered with plasma chemokine ligand, a protein that helps the body recover, leading to diminished gains in fitness. "People tend to think the inflammatory response following exercise is a bad thing because it is painful and temporarily reduces athletic capability," says Crystal. "But it is actually a very important part of recovery and adaptation [and leads to] getting more fit. The inflammatory response, though unpleasant, serves a very important purpose." Previous studies have come to similar conclusions, measuring at best minimal gain for muscle recovery and soreness after of a post-workout ice bath.

Instead of relying on this scientifically controversial practice, stick with the tried-and-true rules for muscle recovery, which include drinking fluids with sodium immediately after (or during) your workout, eating a snack with carbohydrates within 10 minutes, and having a full protein-rich meal within at least two and a half hours.